The invention relates to the internals for a radial flow reactor. A radial flow reactor includes devices for retaining catalyst or adsorbent in a frustoconical space within a reactor, and devices for the inlet and outlet flow of fluid across the catalyst or adsorbent.
A wide variety of processes use radial flow reactors to provide for contact between a fluid and a solid. The solid usually comprises a catalytic material on which the fluid reacts to form a product, or an adsorbent for selectively removing a component from the fluid. The processes cover a range of processes, including hydrocarbon conversion, gas treatment, and adsorption for separation.
Radial flow reactors are constructed such that the reactor has an annular structure and that there are annular distribution and collection devices. The devices for distribution and collection incorporate some type of screened surface. The screened surface is for holding catalyst or adsorbent beds in place and for aiding in the distribution of pressure over the surface of the reactor, or adsorber, and to facilitate radial flow through the reactor bed. The screen can be a mesh, either wire or other material, or a punched plate. For a moving bed, the screen or mesh provides a barrier to prevent the loss of solid catalyst particles while allowing fluid to flow through the bed. The screen requires that the holes for allowing fluid through are sufficiently small to prevent the solid from flowing across the screen. Solid catalyst particles are added at the top, and flow through the apparatus and removed at the bottom, while passing through a screened-in enclosure that permits the flow of fluid over the catalyst. The screen is preferably constructed of a non-reactive material, but in reality the screen often undergoes some reaction through corrosion, and over time problems arise from the corroded screen or mesh.
The screens or meshes used to hold the catalyst particles within a bed are sized to have apertures sufficiently small that the particles cannot pass through. The outer screen element can be provided by a cylindrical screen that retains particles in its interior, and provides for the distribution of fluid through the space between the screen and the outer wall of the reactor. Another design for an outer screen element is to use a plurality of oblong conduits arrayed around the wall of the reactor. A common shape for the oblong conduits is a scallop shaped cross-section where the flattened side is positioned against the wall of the reactor and the more sharply curved side presents a screened face that allows the catalyst to flow against, while fluid flows within the oblong conduit and passes through the screened face. The flattened side is shaped to substantially conform with the curve of the reactor wall to minimize volume between the conduits and the reactor wall.
The common type scallop design can be found in U.S. Pat. Nos. 5,366,704 and 6,224,838, where the scallops have either punched plates or longitudinally extended profile wire arrangements, respectively.
The scallop design provides some improvements in convenience for placing the screen elements in the reactor, but the scallop designs also include the drawback of creating tight spaces where catalyst can lodge and get stuck. The scallop design also presents regions of uneven flow for the fluid entering the region holding the catalyst and therefore provide for poorer utilization of the catalyst within the reactor.